speedo vs gps
Pro
Joined: Oct 2008
Posts: 645
Likes: 1
From: Hayward Wi
I would test out your GPS for accuracy if you can get it out of the car,
and maybe if you can go bug an cop buddy (Ie if you have one) to use his laser pointer speed thing to see if the speedo is off or maybe those roadside speed things
or have an friend drive at an set speed an fallow them and see what you come up with
some ideas anyway
and maybe if you can go bug an cop buddy (Ie if you have one) to use his laser pointer speed thing to see if the speedo is off or maybe those roadside speed things
or have an friend drive at an set speed an fallow them and see what you come up with
some ideas anyway
Racer
Joined: Sep 2008
Posts: 252
Likes: 0
From: San Antonio Texas
I'd vote for the gps being correct.
My dash is like .5mph over the gps or something. sometimes its exact, sometimes not. And my hud always seems to show 1mph faster than my cruise is set. weird.
My dash is like .5mph over the gps or something. sometimes its exact, sometimes not. And my hud always seems to show 1mph faster than my cruise is set. weird.
Former Vendor
Joined: Nov 2005
Posts: 8,995
Likes: 2
From: Spring Texas
St. Jude Donor '08
My Alpine Blackbird has a speedo function on it that always reads about 5-10mph slower than my speedo.
The GPS updates my position about 3-5 times per second but the car's speedo is constantly being updated. I would venture to guess the GPS systems in our cars simply aren't fast enough to update with super-accurate real-time speed.
The GPS updates my position about 3-5 times per second but the car's speedo is constantly being updated. I would venture to guess the GPS systems in our cars simply aren't fast enough to update with super-accurate real-time speed.
Thread Starter
Drifting
Joined: Mar 2007
Posts: 1,589
Likes: 1
From: Leelanau County
thanks again for all the responses
maybe someone in the mooresville, nc area will take me and my gps for a spin in their vette and compare the two gps's. pm me for the spin
Last edited by germanc5; Oct 29, 2008 at 07:52 PM.
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Race Director
Joined: Oct 2002
Posts: 16,477
Likes: 26
From: Gone
CI 6-7-8-9-10 Veteran
St. Jude Donor '03
It's a calculation of speed based off read wheel speed sensor pulses, coupled with (programmable) tire height data.
I've compared both my truck and C5 to GPS, and both are right-on...but if there were a case of substantial difference between the two, I would lean toward GPS as being the more accurate indicator.
There's been many more than one known case of odd values showing up in a stock PCM tune.
